1. Field of the Invention
This invention relates generally to access devices and more specifically to seals and other closure mechanisms applicable to devices.
2. Discussion of the Prior Art
Access devices are commonly used in surgery to facilitate the introduction of various surgical instruments into vessels, conduits, cavities, and other interior regions of the body. These access devices include, for example, devices which facilitate introduction of a needle into a vessel, and trocars which facilitate the introduction of laparoscopic instruments into the abdomen of the body.
Some of these access devices are introduced into regions which include a fluid under pressure. In the case of a needle access device, this fluid may be a liquid such as blood. In the case of a trocar, this fluid may be a gas such as an insufflation gas. In either case it is desirable to provide for the introduction of the surgical instrument into the cavity without permitting the escape of the pressurized fluid.
Seal mechanisms are usually employed in an access device to prevent this escape of fluid. Such mechanisms have typically included an aperture or septum valve which has functioned satisfactorily to form a seal around the outer surface of an instrument positioned within the access device. However, when this instrument has been removed, such aperture or septum valves have been relatively ineffective in providing a complete closure or zero closure to prevent the escape of pressurized fluid. For this reason, a zero closure valve has typically been included in the seal mechanism. While zero closure valves are typically not relied on to seal with an installment in place, they nevertheless are expected to provide an effective closure when the instrument is removed.
In the past, zero closure valves have included flapper valves which permit the instrument to pass through the valve, but which are automatically biased to a closed position when the instrument is removed. One problem with the flapper valve is its complexity which generally equates to expensive and difficult manufacturing processes. An example of the flapper valve is disclosed by Moll et al. in U.S. Pat. No. 4,654,030.
Another type of zero closure valve is commonly referred to as a "duck bill" valve. This particular mechanism can form an effective zero closure, but it suffers from high friction forces which tend to inhibit insertion and removal of the instrument. The duck bill mechanism also tends to invert when the instrument is removed. An example of the "duck bill" valve is disclosed by Edwards, et al, in U.S. Pat. No. 4,566,493.